a. Field of the Invention
This invention relates to a method of producing N-formylamine by photosensitized oxygenation of aldehyde-amine mixture whereupon carbonyl transformation from aldehyde to amine occurs.
b. Description of the Prior Arts
There have been known several methods of producing N-formylamine since the late period of 1950.
Those conventional techniques are as follows:
(1) N-formylamine is produced by the reaction of amine with carbon monoxide at a high temperature and pressure in the presence of a metal catalyst of transition state. PA1 (2) N-formylamine is produced by the reaction of the corresponding amine with formic acid or chloral. PA1 (3) Christopher S. Foote and John Wei-Ping Lin disclosed in Tetrahedron Letters No. 29, pp. 3267-3270, 1968 that the reaction of aldehyde enamines with singlet oxygen affords corresponding ketones and N-formylamine as carbon-carbon cleavage products in quantitative yields.
In this case, however, firstly the enamine should be prepared by reacting aldehyde with amine. Then, the resulted enamine should be separated to be used for the reaction as above mentioned. Therefore, this method includes more steps than the method of the present invention hereinafter mentioned. Also, this method is not suitable to an unstable enamine to be scarcely separated. It is significant that N-formyl piperidine or morpholine could be produced directly by photosensitized oxygenation of aldehyde-amine mixture under mild condition, without separating intermediate enamine.
Dimethylformamine(DMF) and dimethylsulfoxide(DMSO) are high polar aprotic solvents, and are used widely. DMF cannot, however, be used as a solvent at a high temperature reaction about 200.degree. C., because of its boiling point comparatively not higher than N-formylpiperidine (VI) and N-formylmorpholine (III).
Said compounds (III) and (VI) are the homologues of DMF and have almost the same properties concerning chemical property or capability of dissoluting gases and inorganic substance. However, the boiling points of the compounds (III) and (VI) are considerably higher than that of DMF so that the compounds (III) and (VI) are ideal as excellent and non-volatile solvents.
It is important for a solvent to be used that the temperature range of liquid state thereof is broad.
The temperature range of liquid state of (VI) and (III) is wider than that of DMF by about 40.degree. C. This is evident referring to the following table.
Table I ______________________________________ Amide Physical property ##STR1## ##STR2## ##STR3## ______________________________________ Boiling point 153.degree. C. 222.degree. C. 120 .degree. C./15mm Melting point -60 -31 22 Temperature range of liquid 213.degree. 253.degree. about 250 .degree. state ______________________________________
In addition, the characteristic and important property of the compounds (VI) and (III) is the high capability of solubilizing high polymers. The compounds (III) and (VI) are practically used as excellent solvents in the chemical industry of high polymers. The compounds (III) and (VI) are very soluble in hexane as well as water, and easily obtainable by distillation in pure and anhydrous state. The advantage of the compounds (III) and (VI) over DMF is the fairly slower absorption of moisture from atmosphere. Thus, it is understood that the compounds (III) and (VI) are very excellent high polar aprotic solvents and applicable to wider variety than DMF. Therefore, it is significant to synthesize simply and economically the compounds (III) and (VI).